Two important areas of transition metal-protein interactions will be studied. The first of these is the nature of iron-peptide complexes in cases where there is a direct interaction (non-heme iron peptides). The second is the nature of heme-like oxygen carrying analogs. In both cases, simple models of the more complex biochemical systems will be used. Both studies involve the preparation and detailed structural analysis of transition metal complexes which are simple analogs of transition metal protein systems. A variety of physical techniques will be utilized to determine the detailed electronic and molecular structure of these compounds. The structural data thus obtained will be used as a basis for hypotheses regarding the structural nature of the biologically active moieties.